1. Field
The present disclosure relates to an igniter, an igniter control method, and an internal combustion engine ignition apparatus including the igniter.
2. Description of Related Art
There is an increasing demand for improving the “safety”, “comfort”, and “environmental performance” of vehicles. With an increase in the number of electronic components used in the vehicles, the number of semiconductors used per vehicle increases and there is a demand for an in-vehicle semiconductor device with “high reliability”, a “small size”, and a “low cost”. Similarly, a technique has been developed which reduces the size of an internal combustion engine ignition apparatus to reduce the size of an engine or improves energy efficiency to improve fuel efficiency and environment. In addition, it is necessary to increase the amount of current and voltage resistance in order to reduce the size of an igniter forming the internal combustion engine ignition apparatus or to improve the performance of the igniter.
In the related art, a current-detection-type igniter has been mainly used which detects a current on the basis of a voltage drop across a shunt resistor for current detection that is connected in series to an insulated gate bipolar transistor (IGBT; hereinafter, referred to as a main IGBT) for blocking a primary current which flows to the primary side of an ignition coil. However, the sum of a saturation voltage VCE (sat) between the collector and the emitter and a voltage which is generated by the shunt resistor for current detection increases, which results in an increase in the loss of the igniter.
In contrast, in a sense IGBT type in which a sense IGBT that is connected in parallel to the main IGBT detects and controls the current, since the shunt resistor for current detection (sense resistor) is connected in series to the sense IGBT, the shunt resistor for current detection which is connected in series to the main IGBT is not needed. As such, since the shunt resistor for current detection which is connected in series to the main IGBT is not needed, the loss of the igniter does not increase. Therefore, in recent years, the sense IGBT type has been widely used.
Next, the structure of an internal combustion engine ignition apparatus according to the related art will be described. FIG. 9 is a circuit diagram illustrating the circuit structure of a main portion of an internal combustion engine ignition apparatus 500 according to the related art. The internal combustion engine ignition apparatus 500 according to the related art illustrated in FIG. 9 includes an igniter 600, an ignition coil 202, and a spark plug 203. The igniter 600 includes an IGBT unit 51, a control IC unit 52, a battery resistor RB, and a capacitor CBG. The igniter 600 is a multi-chip igniter 601 including a semiconductor chip D1 and a semiconductor chip D2.
The IGBT unit 51 which is formed in the semiconductor chip D1 includes a main IGBT 3, a sense IGBT 4, a depression IGBT 20, a G-C zener diode 5 (G indicates a gate and C indicates a collector), a surge protective G-E zener diode 6 (E indicates an emitter), a diode 7, a resistor 8, a surge protective sense G-E zener diode 9, a surge protective resistor 10, and a surge protective zener diode 11. The sense IGBT 4 and the main IGBT 3 share a collector 3a. 
The depression IGBT 20 is connected between the collector 3a and a gate 3b of the main IGBT 3. The depression IGBT 20 has a function of increasing the gate potential of the main IGBT 3 to suppress the oscillation of a collector current Ic of the main IGBT 3. The G-C zener diode 5 is connected between the gate 3b and the collector 3a of the main IGBT 3. The G-C zener diode 5 has a function of clamping a collector voltage VCE of the sense IGBT 4 and the main IGBT 3. The G-E zener diode 6 is connected between the gate 3b and an emitter 3c of the main IGBT 3.
The diode 7 is connected between the emitter 3c of the main IGBT 3 and an emitter 4c of the sense IGBT 4. The diode 7 has a function of setting the emitter voltage of the sense IGBT 4 to be higher than the emitter voltage of the main IGBT 3. The diode 7 is an asymmetric bidirectional zener diode in which different series of zener diodes are connected in inversely parallel to each other. The resistor 8 is connected between the gate 3b of the main IGBT 3 and a gate 4b of the sense IGBT 4. The resistor 8 has a function of setting the gate voltage of the sense IGBT 4 to be lower than the gate voltage of the main IGBT 3.
The sense G-E zener diode 9 is connected between the gate 4b and the emitter 4c of the sense IGBT 4. One end of the resistor 10 is connected to a connection point 8a among the gate 3b of the main IGBT 3, the G-C zener diode 5, and the resistor 8. The zener diode 11 is connected between the other end of the resistor 10 and the ground. A connection point 11a between the resistor 10 and the zener diode 11 is connected to a gate terminal GATE of the control IC unit 52. In addition, the emitter 4c of the sense IGBT 4 is connected to a sense terminal SNS of the control IC unit 52.
The control IC unit 52 which is formed in the semiconductor chip D2 includes, for example, a sense resistor Rsns, a sense terminal SNS, the gate terminal GATE, a battery terminal BM, a control terminal SIN, and a ground terminal GND. For example, a current limiting circuit and an overheat detection circuit which are not illustrated are formed in the control IC unit 52. A sense current Isns flows to the sense resistor Rsns and a sense voltage Vsns is generated.
The battery terminal BM is connected to a battery terminal B of the multi-chip igniter 601 through a battery resistor RB. A connection point between the battery resistor RB and the capacitor CBG is connected to one end of the ignition coil 202. The control terminal SIN of the control IC unit 52 is connected to a control terminal S of the multi-chip igniter 601. The ground terminal GND of the control IC unit 52 is connected to a ground terminal G of the multi-chip igniter 601.
The collector 3a of the main IGBT 3 is connected to a collector terminal CM of the IGBT unit 51. The collector terminal CM is connected to a collector terminal C of the multi-chip igniter 601. The collector terminal C of the multi-chip igniter 601 is connected to the primary end of the ignition coil 202. The secondary end of the ignition coil 202 is connected to one end of the spark plug 203. The other end of the spark plug 203 is connected to the ground.
Next, the arrangement of the main IGBT 3 and the sense IGBT 4 in the IGBT unit 51 forming the multi-chip igniter 601 (conventional product) according to the related art will be described. FIG. 10 is a plan view illustrating the planar arrangement of the main IGBT 3 and the sense IGBT 4 illustrated in FIG. 9. FIG. 10 illustrates two conventional products (hereinafter, referred to as conventional products No. 1 and No. 2). The conventional products No. 1 and No. 2 are different from each other in a distance L between the sense IGBT 4 and the main IGBT 3. In FIG. 10, the conventional products No. 1 and No. 2 are illustrated in one figure in order to clarify the difference in the distance L between the sense IGBT 4 and the main IGBT 3. However, the conventional products No. 1 and No. 2 are examples of different multi-chip igniters 601. That is, the conventional products No. 1 and No. 2 each include one sense IGBT 4 and one main IGBT 3. Of two sense IGBTs 4 illustrated in FIG. 10, the right sense IGBT is the sense IGBT 4 of the conventional product No. 1 and the left sense IGBT is the sense IGBT 4 of the conventional product No. 2.
As illustrated in FIG. 10, the main IGBT 3 has, for example, a concave polygonal shape in a plan view in which at least one interior angle (reentrant corner) is greater than 180 degrees. The sense IGBT 4 is arranged so as to face two sides that form the interior angle of the main IGBT 3. Specifically, in the product No. 1 according to embodiments of the invention described later in this disclosure, for example, the distance L between the sense IGBT 4 and one of the sides that form the interior angle of the reentrant corner of the main IGBT 3 is about 150 μm. But in both the conventional products No. 1 and No. 2 , the sense IGBT 4 is arranged so as to be a predetermined distance L away from one of the sides of the main IGBT 3 that form the interior angle of the reentrant corner and so as to be close to the other side forming the interior angle of the reentrant corner. In the conventional product No. 1, the distance L between the sense IGBT 4 and the main IGBT 3 is 800 μm. In the conventional product No. 2, the distance L between the sense IGBT 4 and the main IGBT 3 is 1000 μm.
In FIG. 10, in some cases, a p+ extraction region 4e which is represented by a dotted line so as to surround the sense IGBT 4 is provided in order to extract an excessively large amount of hole current which flows from the main IGBT 3 to the sense IGBT 4 and to increase a sense ratio (=the collector current Ic/the sense current Isns).
Next, the operation of the internal combustion engine ignition apparatus 500 illustrated in FIG. 9 will be described. A voltage is applied from the battery terminal B to the control IC unit 52. The voltage is a power supply voltage of the control IC unit 52. In addition, the voltage is applied from the battery terminal B to the main IGBT 3 through the ignition coil 202 and the collector terminal CM of the IGBT unit 51.
First, the normal operation of the internal combustion engine ignition apparatus 500 will be described. When an on control signal is input from an engine control unit (ECU) (not illustrated) to the control terminal S of the multi-chip igniter 601 forming the internal combustion engine ignition apparatus 500, the control signal is applied to the control terminal SIN of the control IC unit 52. When the control signal is input to the control terminal SIN, the control IC unit 52 processes the signal. Then, a gate signal is input from the gate terminal GATE of the control IC unit 52 to the gate 3b of the main IGBT 3 through the resistor 10 of the IGBT unit 51 and is also input to the gate 4b of the sense IGBT 4 through the resistor 8.
When the gate signal is input to the main IGBT 3 and the sense IGBT 4 at the same time, the main IGBT 3 and the sense IGBT 4 are turned on at the same time. Then, the collector current Ic, which is a main current, flows from the battery terminal B to the main IGBT 3 through the ignition coil 202 and the sense current Isns flows to the sense IGBT 4. Since the sense current Isns flows to the ground through the sense resistor Rsns, the sense voltage Vsns is generated at both ends of the sense resistor Rsns. The sense voltage Vsns is input to the control IC unit 52 and is processed by a logic circuit (not illustrated). An optimum gate signal is output from the gate terminal GATE.
On the other hand, when an off control signal is input to the control terminal S of the multi-chip igniter 601, the main IGBT 3 and the sense IGBT 4 are turned off at the same time. When the main IGBT 3 is turned off, the collector current Ic which flows to the main IGBT 3 through the ignition coil 202 is blocked and a high voltage is generated on the secondary side of the ignition coil 202 by induced electromotive force (=L×dlc/dt) which is generated by the inductance L of the ignition coil 202 and the rate of change of current dlc/dt. When the high voltage is applied to the spark plug 203, an electric discharge occurs in the spark plug 203 and the air-fuel mixture in a fuel chamber (not illustrated) is ignited. When energy stored in the ignition coil 202 is emitted, the flame is extinguished by the extinction operation of the spark plug 203.
Next, an abnormal operation of the internal combustion engine ignition apparatus 500 will be described with reference to FIG. 12 which will be described below. When overcurrent flows to the main IGBT 3 due to any error, the sense voltage Vsns which is generated at the sense resistor Rsns of the control IC unit 52 increases. Therefore, a current limiting circuit (not illustrated) of the control IC unit 52 processes the sense voltage Vsns to reduce a gate voltage VGE output from the gate terminal GATE, thereby suppressing the collector current Ic which flows to the main IGBT 3 to an overcurrent limiting current value Io.
In this case, when the collector current Ic is greater than the overcurrent limiting current value Io, the gate voltage VGE is reduced and the collector current Ic is rapidly reduced to the overcurrent limiting current value Io through a peak value Ip. When a difference (drop) between the peak value Ip and the overcurrent limiting current value Io is large, the overshoot of the collector current Ic increases and the collector voltage VCE oscillates greatly. The secondary voltage of the ignition coil 202 increases due to the large oscillation of the collector voltage VCE and an ignition error occurs in the spark plug 203.
In order to suppress the overshoot of the collector current Ic caused by the oscillation of the collector voltage VCE, a depression IGBT 20 is provided in the igniter 600, as illustrated in FIG. 9 (for example, see JP 9-280147 A). When the depression IGBT 20 is used as a constant current circuit, the gate voltage VGE of the main IGBT 3 increases. When the gate voltage VGE increases, the overcurrent limiting current value Io increases and the overshoot of the collector current Ic of the main IGBT 3 is reduced. Therefore, the oscillation of the collector voltage VCE is suppressed. As a result, the secondary voltage of the ignition coil 202 is suppressed and an ignition error in the spark plug 203 is prevented.
In the depression IGBT 20, the gate and the emitter are short-circuited to form a constant current circuit. In the multi-chip igniter 601 illustrated in FIG. 9, the IGBT unit 51 and the control IC unit 52 are formed in different semiconductor chips D1 and D2 and the semiconductor chips D1 and D2 are fixed to, for example, a lead frame or a ceramic substrate with a conductive pattern which is not illustrated.
Next, patent documents related to the igniter will be described. First, JP 9-280147 A discloses the following content. In an igniter having a protective circuit, when the flow of a current to an IGBT is blocked due to an error, such as overcurrent, a collector current of the IGBT flows to a sense resistor through a sense IGBT to detect a potential difference. When the detected potential difference is greater than a predetermined value, the gate voltage of the IGBT is reduced to suppress an increase in the current of the IGBT.
At that time, in a MOS gate (metal-oxide-semiconductor insulated gate) element, such as an IGBT, a saturation current is constant with respect to the collector voltage. Therefore, when the gate voltage is reduced, the current of the IGBT is rapidly reduced to a value corresponding to the reduced gate voltage. An induced electromotive force is generated in the coil by the rapid reduction in the current and the collector voltage of the IGBT increases rapidly. The current of the IGBT is reduced by the rapidly increased collector voltage. The reduction in the current of the IGBT is detected and the gate voltage increases rapidly again in order to make the current flow to the IGBT. Then, the collector voltage is rapidly reduced. This operation is repeated and the collector voltage oscillates. The voltage of the spark plug is higher than a discharge voltage according to the collector voltage during the oscillation, which causes an ignition error.
In order to solve this problem, a depression IGBT which is a constant current source is inserted between the collector and gate of the IGBT. When the gate voltage is reduced during the detection of overcurrent, the constant current source increases the gate voltage with the increase in the collector voltage, thereby compensating for the reduction in the gate voltage. That is, the rate of decrease of the gate voltage is reduced and the gate voltage is gently reduced. Therefore, the rate of decrease of the current of the IGBT is reduced and the current is gently reduced. As a result, the oscillation of the collector voltage is suppressed. It is possible to prevent an ignition error in the spark plug.
JP 2009-117786 A discloses the following content. JP 2009-117786 A discloses a one-chip igniter in which a main IGBT, a sense IGBT, a depression IGBT, and a protective circuit (corresponding to the control IC unit illustrated in FIG. 9) are provided in one chip. The sense IGBT is arranged close to the main IGBT (=800 μm). In this case, when an error occurs (for example, when overcurrent is generated), the current of the main IGBT flows to the sense IGBT, a large voltage drop occurs across a sense resistor, and the current of the main IGBT which is significantly greater than the actual current value is detected. In this case, the current of the main IGBT is reduced to a predetermined current value or less by the detected excessively large voltage drop across the sense resistor and the protective circuit performs a process of reducing the gate voltage at the gate terminal of the main IGBT such that the current of the main IGBT is reduced.
When the gate voltage of the main IGBT is reduced, the current of the main IGBT is reduced and the current which flows to the sense IGBT is also reduced. Then, since a voltage drop across the sense resistor is small, the protective circuit increases the gate voltage of the main IGBT such that the current of the main IGBT increases. Therefore, the current of the main IGBT increases. This feedback operation is repeated and the collector current of the main IGBT oscillates. When the collector current oscillates, an induced electromotive force is generated by the inductance of the ignition coil. Therefore, the collector voltage oscillates with a large amplitude and an ignition error occurs in the spark plug.
In contrast, in the structure in which the distance between the main IGBT and the sense IGBT is equal to or greater than 1500 μm, the current of the main IGBT flows to the sense IGBT when an error occurs and the voltage drop across the sense resistor does not overlap. Therefore, the collector voltage does not oscillate and it is possible to prevent the occurrence of an ignition error in the spark plug.
The amount of current (hole current) which flows from the main IGBT to the sense IGBT is reduced and the oscillation of a current waveform during soft turn-off is suppressed. The term “soft turn-off” is softly turning off the collector current of the main IGBT when an error occurs, such as when overcurrent is generated, to suppress a rapid increase in the collector voltage.
The following JP 7-245394 A discloses the following content. A main IGBT includes a sense IGBT with an overcurrent detection function. The sense IGBT is surrounded by a p well region for extracting holes. In particular, in FIG. 2 described in the following JP 7-245394 A, a sense IGBT region which has a substantially rectangular shape in a plan view and is which a plurality of sense IGBTs are arranged is adjacent to the main IGBT at the shortest distance in three directions which are perpendicular to three sides of the sense IGBT region. In one direction that is perpendicular to the remaining one side of the sense IGBT region, the sense IGBT region is arranged at a distance that is sufficiently greater than the shortest distance from the main IGBT and is adjacent to the main IGBT, with a p well region interposed therebetween. When the shortest distance between the sense IGBT region and the main IGBT is equal to or greater than 100 μm, the dependence of the sense ratio on the voltage is constant.